A burst water main that flooded an electrical substation has caused power outages across the Adelaide CBD, affecting businesses, a hospital and a school.SA Water crews have been on Grenfell Street to repair a water main break since 2am on Friday.SA Power Networks (SAPN) said the burst main flooded a substation in Coromandel Place."We have a substation in Coromandel Place, which is essentially across from Rundle Place Shopping Centre, and the water from that burst main has essentially flooded part of the Coromandel Place substation and that has, of course, triggered safety equipment," SAPN's Cecilia Schutz told 891 ABC Adelaide.SA Water says repair works in Adelaide's CBD are expected to continue throughout the day. (ABC News: Ben Pettitt)An SAPN spokesperson said safety mechanisms activated within the substation to shut it down, causing an outage for approximately 1,200 city customers.The spokesperson said the Calvary Hospital was affected but "as a matter of priority" electricity was restored by 8:12am.They said crews were able to "reroute" other power supplies to restore electricity to 600 customers but as at 8:15am, more than 500 remained without power.Cecilia Schutz says it is an unusual occurrence. (ABC News: Sophie Landau)"We do hope to make progress throughout the day but … it will take some days before this substation is operational again," Ms Schutz said."This is the first time that I have seen in many years a flooding incident in a substation in the CBD — this is an unusual circumstance, yet we are prepared for it through contingency, but electricity and water never mix and the safety of our crews and the community is of paramount importance."As at 7:30am, traffic restrictions were in place on Grenfell Street, with the northbound left bus lane closed between Gawler Place and Twin Street.The SA Department for Education closed Adelaide Botanic High School for the day, as the school, with about 1,200 students, was also left without power."Following an assessment of the situation and in order to ensure student and staff safety, a decision has been made to close the school for the day," an education department spokesperson said."Parents are being advised of the situation by the school."Businesses like shops in Rundle Place are without power. (ABC News: Ben Pettitt)'Some time' before power, water restoredSA Water General Manager David Coombe said it was supporting Rundle Place shopping mall, which is currently without water."There's some high voltage power that we're dealing with here on Grenfell Street and a lot of other services underground which slows our ability to be able to repair it quickly," he said."We have a vacuum truck here at Grenfell Street and certainly at the substation extracting the water. Unfortunately, we've had inundation into one property within the Rundle Plaza."Mr Coombe said it was "quite a complex repair"."We're working as quickly as we can but we expect it could be into the early hours of the evening before we'll be able to finalise repairs," he said.He said early indications were that it appeared that there had been a split in the pipe."Quite often at this time of year with changing soil conditions, movement of soil, we can see that water mains do break — the pipe moves and soil moves away from the water main, we lose a bit of support there, but it looks as though the pipe has split," Mr Coombe said.Work is underway to restore power and water across the CBD. (ABC News: Ben Pettitt)An SA Water spokesperson said they were helping SAPN to assess the damage and required repairs, while their crews were also on site "supporting impacted customers and property owners"."The incident was reported during the early hours of this morning, with a field technician arriving on site at approximately 2am to begin turning the water off," an SA Water spokesperson said."The break has resulted in water entering several nearby properties and facilities, including some basements or underground areas."An SAPN spokesperson said flooding to the substation meant it would "not be safe for SA Power Networks to restore power to the substation for some time"."We continue to work on finding alternate supply for customers who remain affected by the outage but we are urging city workers whose offices are affected to work from home if that is possible," the spokesperson said."We will be moving mobile generation into the areas of most critical need. We aim to restore supply to all customers by the end of today and we will continue to provide updates as this work progresses."